A 34-year-old woman with obsessive-compulsive disorder, contamination subtype, has been attending weekly CBT sessions for six weeks. She reports spending approximately three hours daily washing her hands and avoiding public restrooms entirely. The PMHNP has completed psychoeducation about the OCD cycle and collaboratively developed a fear hierarchy with the patient. The patient now asks what the next step in treatment will involve. Which of the following best describes the core therapeutic mechanism of exposure and response prevention (ERP) for this patient?